Evolution of Fault-Zone Hydromechanical Properties in Response to Different Cementation Processes

Abstract

Progressive cementation and sealing of fault-localized fractures impact crustal mass transport and the recovery of fault strengthfollowing slip events. We use discrete fracture network (DFN) models to examine how fracture sealing during end-membercementation mechanisms (i.e., reaction-versus transported-limited cementation) influences the partitioning of fluid flowthrough time. DfnWorks was used to generate randomized fracture networks parameterized with fracture orientation datacompiled from field studies. Single-phase flow simulations were performed for each network over a series of timesteps, andnetwork parameters were modified to reflect progressive fracture sealing consistent with either reaction or transport-limitedcrystal growth. Results show that when fracture cementation is reaction-limited, fluid flow becomes progressively channelizedinto a smaller number of fractures with larger apertures. When fracture cementation is transport-limited, fluid flow experiencesprogressive dechannelization, becoming more homogeneously distributed throughout the fracture network. These behaviors areobserved regardless of the DFN parameterization, suggesting that the effect is an intrinsic component of all fracture networkssubjected to the end-member cementation mechanisms. These results have first-order implications for the spatial distributionof fluid flow in fractured rocks and recovery of permeability and strength during fault/fracture healing in the immediateaftermath of fault slip.